public class myStudent {
    public static void main(String[] args) {
        System.out.println("任务一");
        int x=6,y=2,c;
        if (x<0 && y<0)
            System.out.println("数字有误");
        else {
            c=x*y/2;
            System.out.println(c);
        }
    }
}
